(a) Explain the term drift velocity of electrons in a conductor .Hence obtain the expression for the current through a conductor in terms of drift velocity.
(b) Two cells of emfs E 1 and E 2 and internal resistances r 1 and r 2 respectively are connected in parallel as shown in the figure. Deduce the expression for the
(i) equivalent emf of the combination
(ii) equivalent internal resistance of the combination
(iii) potential difference between the points A and B.